以染色体断裂同源重组修复为靶点增高乳腺癌细胞对PARP1抑制剂的敏感性

Poly (ADP-Ribose) Polymerase 1 (PARP1) inhibitor which can prevent the repair of DNA single strand breaks and target cells deficient in DNA double strand breaks repair, exhibit highly selective killing of BRCA1 or BRCA2 mutated tumor cells while maintaining minimal toxicity in normal tissues. However, only 5-10% of all cases of breast cancer belong to BRCA mutation associated family breast cancer are sensitive to PARP1 inhibitor. Our preliminary data has demonstrated that BRCA1 is a nuclear and cytoplasm shuttling protein and Homology-Recombinational(HR) directed DNA double strand breaks repair depend on the function of nuclear BRCA1; We also found that radiation treatment and truncated BRCA1 peptide can induce BRCA1 nuclear export. This project will study the sensitization of PARP1 inhibitor through inducing BRCA1 nuclear export. First, we will Determine if BRCA1 nuclear export is the required mechanism for radiation to convert BRCA1-proficient breast cancer cells to become highly susceptible to PARP1 inhibitor, then use cell line and nude mice model to validate that radiation and truncated BRCA1 peptide can induce BRCA1 nuclear export, reduce HR-mediated repair and sensitize breast cancer cells (with wild-type BRCA1) to PARP1 inhibitor.

聚腺苷二磷酸核糖基聚合酶1（Poly(ADP-Ribose)Polymerase1,PARP1）抑制剂抑制DNA单链断裂修复，是DNA双链断裂修复缺陷细胞的靶向药物，高度选择性杀伤携带BRCA1或BRCA2突变的肿瘤细胞，对正常组织毒性很小。然而，只有5-10%乳腺癌是BRCA突变相关的家族性乳腺癌，对PARP1抑制剂敏感。我们的前期工作发现BRCA1是一个胞核胞浆穿梭蛋白，同源重组介导的DNA双链断裂修复需要胞核BRCA1；放射处理和BRCA1截短蛋白肽可诱导BRCA1出核。本项目拟探讨诱导BRCA1出核对PARP1抑制剂的增敏作用，先明确BRCA1出核是BRCA1功能完好的乳腺癌细胞成为PARP1抑制剂高度敏感细胞的必需机制，然后在细胞水平和裸鼠移植瘤水平证实放射和BRCA1截短蛋白肽可诱导BRCA1出核，减少同源重组修复,增高携带野生型BRCA1的乳腺癌细胞的PARP1抑制剂敏感性。

PARP抑制剂是正在广泛研究的潜在的治疗乳腺癌和卵巢癌的口服化疗药物。主要用于治疗BRCA1或BRCA2突变相关的肿瘤。本研究通过转染MCF7细胞三个穿梭功能不同的BRCA1表达载体后的放射诱导BRCA1出核情况、同源重组修复能力和PARP1抑制剂敏感性，然后研究出核转运抑制剂Leptomycin B抑制BRCA1出核对PARP1抑制剂敏感性的降低作用，以及BRCA1截短蛋白肽促进BRCA1出核对PARP1抑制剂的增敏作用，证明了BRCA1出核是BRCA1功能完好的乳腺癌细胞成为PARP1抑制剂高度敏感细胞的必需机制。最后通过细胞和裸鼠移植瘤实验证实放射可诱导BRCA1出核，增高BRCA1和p53功能完好的散发性乳腺癌细胞的PARP1抑制剂敏感性。

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